Kerstin Kvist enters crumbling Lydstep Old Hall to live with the Cosways and to act as nurse to John, a grown man fed drugs by his family to control his lunatic episodes. But John's strangeness is grotesquely mirrored in that of his four sisters who roam the dark, mazy Essex country house under the strict gaze of eighty-year-old Mrs Cosway. Despite being treated as an outsider, Kerstin is nevertheless determined to help John. But she soon discovers that there are others in the family who are equally determined that John remains isolated, for sinister reasons of their own ...